Chemical oscillation in electrochemical oxidation of methanol on Pt surface

Based on dual path reaction mechanism, a nonlinear dynamics model reflecting the potential oscillation in electrooxidation of methanol on Pt surface was established. The model involves three variables, the electrode potential (e), the surface coverage of carbon monoxide (x), and adsorbed water (y). The chemical reactions and electrode potential were coupled together through the rate constant k _i = exp(a _i (e-e _i )). The analysis to the established model discloses the following: there are different kinetics behaviors in different ranges of current densities. The chemical oscillation in methanol electrooxidation is assigned to two aspects, one from poison mediate CO of methanol electrooxidation, which is the induced factor of the chemical oscillation, and the other from the oxygen-containing species, such as H₂O_a. The formation and disappearance of H₂O_a deeply depend on the electrode potential, and directly cause the chemical oscillation. The established model makes clear that the potential oscillation in methanol electrooxidation is the result of the feedback of electrode potential e on the reactions involving poison mediates CO and oxygen-containing species H₂O_a. The numerical analysis of the established model successfully explains why the potential oscillation in methanol galvanostatic oxidation on a Pt electrode only happens in a certain range of current densities but not at any current density.